The overall goal of the proposed research is to provide a specific, practical means for inactivating C5a in patients at risk of adult respiratory distress syndrome (ARDS). C5a is a key contributory, possibly necessary factor in the pathological course of ARDS. The proteins capable of inactivating C5a noted in the literature are poorly characterized. Synergen's scientists have selected one of these proteins to isolate from human tissue, then characterize its mode of action. An assay based on this biological activity will be used to purify, characterize, clone and express the protein by recombinant DNA technologies. By reducing the action of C5a in patients at risk for ARDS, we expect that the protein will provide a useful therapeutic agent for prevention or amelioration of the pathology.